In a system disclosed in patent literature 1, wiring pattern information, wiring restriction information, and board information are input, and a check result list and a non-connected section list are output. That is, the system reads design data of a printed wiring board, and then detects, for each design rule check item that has been designated as a design rule in advance, parts and contents which do not satisfy a designated threshold value, and indicates these parts and contents as an error message.
Patent literature 2 discloses a technique for regarding design rule check items for improving electromagnetic characteristics as “items that do not necessarily need error correction”, and extracting important errors among these items. According to this system, a design rule check is performed based on wiring information indicating the wiring pattern of each net and design rules indicating constraints of the wiring patterns, and based on the results, screening processing is performed to display the presence or absence of errors for each operating frequency of each net. In short, errors are classified into levels by the operating frequency of the net.
Patent literature 3 discloses level classification of these errors. Patent literature 3 discloses a technique of classifying the risk for the electromagnetic characteristics into levels for each wire in a system for checking positions where a wire crosses a slit or the like of a plane conductor. According to this system, a wire and a plurality of plane conductor layers of a check target are extracted from a CAD data, their projection overlapping are detected, and an attribute of each plane conductor layer is also judged. The wire which crosses between the similar plane conductor layers and the wire which crosses between the different plane layers are classified, different coefficients are added, and each efficient is multiplied by the number of times that the slit and the like are crossed, to digitize the risk level for each wire. As a result, the degrees of influence by the wire crossing between the plane conductor layers are classified by the levels depending on the kind of plane conductor layers and the number of times of crossing.